Is the salary lawful (halal) or unlawful (haram) for working as a pharmacy assistant in a pharmacy that sells painkilling and narcotic pills abused by addicts as an alternative to tramadol, and is it permissible to sell them to a customer if I suspect they are an addict?

It is forbidden to sell narcotic drugs except with a medical prescription. The physician may only prescribe them in cases of extreme necessity and when no permissible alternative is available.

The Permanent Committee for Issuing Fatwas has permitted the use of "Pethidine" or "Morphine" to alleviate pain when necessary, if no permissible alternative is available, provided that it does not lead to a greater harm such as addiction.

It is prohibited to circulate any drug known by experience or by the expertise of trustworthy individuals to be intoxicating or narcotic, except with a medical prescription, even if the state has not classified it as such. However, if its narcotic nature is not known, the original ruling is that its sale is permissible, unless it is highly probable that the buyer is purchasing it for an unlawful purpose, based on the words of Allah Almighty: ﴿And cooperate in righteousness and piety, but do not cooperate in sin and aggression.﴾ Accordingly, it is not permissible to sell medication to someone who is highly suspected of using it for addiction.